The present invention relates generally to a web press into which a web of sheet material is fed from a roll located within an unwind station. More specifically, the invention relates to a mechanism for laterally positioning and adjusting the roll within the unwind station.
In a typical web press, the web of material is supplied from a large roll carried on a shaft that is supported for rotation within an unwind station. Due to the great weight of the roll, typically on the order of 1800 pounds (800 kg), the unwind station is usually provided with a mechanism for lowering a used roll to the floor and then, following initial positioning of a new roll, raising the new roll into operating position.
It is important that the roll be located within the unwind station in a proper lateral position. All further operations to be carried out upon the web, such as printing, perforating, folding and the like, will be placed in a lateral location with respect to the web depending upon the lateral positioning of the roll. The machines within the press for carrying out such operations are normally provided with their own lateral adjustment mechanisms. However, in the event the overall lateral position of the web requires adjustment, it is much simpler to adjust the roll rather than each of the machines within the press. Similarly, when it is necessary to change a roll during press operation, it is highly desirable that the new roll be positioned in the same lateral location as the used roll, to avoid having to reposition all other machines within the press.
In one type of unwind station, the shaft upon which the roll is carried is supported near each end by arms which may be pivotally raised and lowered by a pneumatic or hydraulic cylinder or the like. A wheel is carried at one end of the roll shaft, the wheel having a recess defined entirely around the outer, peripheral edge of the wheel. Mounted to the side frame of the press is a block which has a pivotally connected member that can be moved into engagement with the recess of the shaft wheel when the shaft is located in its operating position. The block is connected to the frame by a mechanism which permits lateral adjustment of the block with respect to the frame. When the pivotal member is engaged with the shaft wheel recess, movement of the block results in lateral adjustment of the shaft and hence of the roll. Also, engagement of the pivotal member and the wheel recess serves to secure the shaft in its proper position without affecting its rotational performance.
While such an adjustment mechanism is effective for changing lateral position of the roll once it is installed within the unwind station, the described mechanism has several disadvantages relating to the installation or removal of a roll. Prior to lowering of a used roll from the unwind station, the lateral adjust mechanism must be disengaged from the shaft wheel. More importantly, once a new roll has been installed, the press operator may have to push the roll laterally until it is engageable with the adjust mechanism, which can be quite difficult due to the weight of the roll. Alternatively, the operator can move the adjust mechanism to the lateral position which the roll occupies, after which the mechanism can be used to readjust the roll to the desired position.
Either operation is relatively time consuming, increasing the non-productive time required for changing of the roll. Moreover, if the mechanism is readjusted to position the new roll, it is possible that the new roll may be placed slightly out of position. Unfortunately, this condition may be discoverable only after some of the web material has been used.
What is needed, therefore, is a lateral adjust mechanism for the roll shaft that not only enables lateral adjustment of the roll, but that positions the roll as it is installed within the unwind station. To increase the speed and efficiency of the roll changing operation, such a mechanism should accurately position the roll automatically as it is lifted into place.